The surface of injection-molded TPE material products turns white – is the problem with the mold or the raw material?

The whitening of the surface of injection-molded TPE material products is a quality problem that troubles many professionals in the manufacturing industry.  It not only reduces the aesthetic quality of the product but may also raise concerns about its performance. Faced with this situation, many people wonder whether the whitening problem stems from a poor mold condition or problems with the TPE raw material itself. In fact, both of these factors can induce whitening, and a step-by-step investigation of production details is needed to determine the cause. So, do you know how to do this? Let's hear the detailed analysis from the editor of Huizhou Zhongsuwang.

I. Whitening Problems Potentially Caused by Raw Materials

The inherent characteristics or differences in the formulation of TPE raw materials are common causes of whitening in TPE products.

An inappropriate proportion of additives in the raw material can cause some components to migrate to the surface of the product during injection molding, forming a white, hazy layer.

Insufficient purity of the raw material, containing too many impurities or inadequately mixed fillers, can result in these components being exposed on the surface after molding, leading to a whitening effect.

Poor compatibility between different components makes it difficult for them to blend uniformly during processing, and phase separation occurs after cooling, manifesting as surface whitening.

If the whitening phenomenon significantly improves after switching to a batch of stable-quality raw materials, it is highly likely that the problem is related to the raw materials.

II. Whitening Causes Related to the Mold

The design, precision, or condition of the mold can also indirectly lead to surface whitening of TPE products.

Improper mold temperature settings: When the temperature is too low, the TPE raw material cools too quickly in the mold cavity, preventing the surface from leveling properly, easily forming small crystals or stress concentrations, which then leads to whitening.

Insufficient surface finish of the mold: Scratches, stains, or mold release agent residue can affect the adhesion between the raw material and the mold, leaving white marks on the surface after molding.

Unreasonable mold venting structure design: During injection molding, the gas in the mold cavity cannot be discharged in time. After the bubbles burst, white spots or a matte surface are formed on the surface of the TPE product. If the whitening problem is alleviated after cleaning, heating, or optimizing the venting structure of the mold, then mold-related factors are more likely to be the cause.

III. Quick Troubleshooting and Solutions

To accurately identify the root cause of TPE material product whitening, a simple comparative test can be used for gradual troubleshooting.

Keep the mold and process parameters unchanged, and try producing with TPE raw materials of known stable quality to observe whether the whitening phenomenon improves.

Keep the raw materials and process parameters unchanged, and try producing after cleaning, adjusting the temperature, or optimizing the venting of the existing mold, and compare the results before and after.

If a single adjustment does not have a significant effect, you can simultaneously optimize the raw materials and mold conditions, and narrow down the problem scope based on the trial production results.

In short, the causes of surface whitening in TPE material products are not singular; both raw materials and molds can be key factors.  Through targeted comparative testing during production, the root cause of the problem can be quickly identified. Then, by adjusting the raw material formula, optimizing the mold condition, or adjusting process parameters based on the actual situation, the whitening problem of TPE products can be effectively improved.